Light-modulated 0-π transition in a silicene-based Josephson junction

Xingfei Zhou; Guojun Jin

doi:10.1103/PhysRevB.94.165436

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Light-modulated 0-π transition in a silicene-based Josephson junction

Xingfei Zhou, Guojun Jin

DOI 10.1103/PhysRevB.94.165436 · Physical Review B

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Abstract

We investigate the Andreev bound states (ABSs) and Josephson current in a silicene-based superconductor-normal-superconductor junction modulated by a perpendicular electric field and an off-resonant circularly polarized light. Based on the Dirac–Bogoliubov–de Gennes equation, we analytically derive the ABS levels and show they have different phase-difference dependences, which will remarkably influence the velocity of Cooper pairs and then the Josephson current. In the pristine or gated silicene, the ABS levels always show negative slope, which means that the Josephson current is irreversible because of the time-reversal symmetry. When an off-resonant circularly polarized light is applied, whether or not there is a perpendicular electric field, the ABS levels will have positive slope, leading to the emergence of reversed Josephson current due to the nonzero center-of-mass wave vector of Cooper pairs. In this light-modulated silicene-based Josephson junction, valley polarization provides an alternative mechanism for 0-π transition, very different from that for the conventional ferromagnetic Josephson junctions where the spin polarization is essential.